experimental study of air injection effect on a surface to prevent ice formation

In order to prevent the ice-accretion on the airfoil surface, an experimental study was conducted to investigate effect of injecting surrounding air from the surface into the main flow. for this purpose, holes were created at the leading edge of the airfoil. five parameters of diameter, pitch, angle of position, hole arrangement, and velocity of the outlet flow from the holes were sought. using principles of experimental design by two-level fractional factorial method,the required tests were designed and determined. conducting tests, the results indicated the injection method significantly reduces weight of ice accreted on the surface. the highest amount of ice mass reduction in experiments reached 85% of the ice mass accreted on the simple airfoil. the diameter and pitch of holes had greatest effect on reducing the mass of ice accreted on the surface, followed by the injection airflow rate and the angle of alignment. therefore, the injection of air at lower temperature than freezing point is as effective for ice accretion and saves energy rather than using hot-air injection. moreover, the injected air from holes created a protective layer around the surface, which enhanced the process.